Aircraft, both fixed-wing and rotary wing, have primary instruments that provide information to their pilots and crew members regarding flight or other situational information of aircraft conditions, such as attitude, altitude, airspeed, and slip. Because primary instruments can fail, aircraft often have back-up instruments.
In general, such back-up instruments have limited functionality and operate only when the primary instruments fail. They must be mounted within the aircraft in a particular location and orientation in order to operate properly, regardless of the practicalities of the cockpit or the preferences of the pilot or crew. They can be rendered inoperable if upgrades to software or changes to settings are written over the onboard software or settings and are interrupted before they are completed. Updating onboard software can require that the back-up instruments be removed from the aircraft and returned to the manufacturer. Because the ARINC 429 data transfer standard used in aircraft does not assign a data label to barometric pressure, direct communication of barometric pressure data from primary instruments to back-up instruments is not possible, thereby requiring that the pilots or crew members manually enter barometric pressure data. Displays have minimally adjustable brightness levels, which are either directly determined by the aircrafts' lighting buses or manually adjusted by the pilots or crewmembers. Though they use color-coding to indicate operational ranges, such as safe (often indicated by green), warning (yellow), and unsafe (red), existing back-up instruments have fixed color-coding, and in newer back-up instruments it is selectable solely based on aircraft type. More, specifically, users identify their aircraft type to the instruments, and the instruments responds by adjusting the color coding to reflect the operational ranges for the identified aircraft type. Unfortunately, this requires that the operational ranges of all possible aircraft types be stored onboard the back-up instruments, which can be impractical and, furthermore, does not accommodate users' preferences.